SIA
xs
sia
Implementation of an XML Schema describing a Simple Image
Access Service. Based on "The Simple Image Access Specification"
by Doug Tody et al.
an abstract capability that fixes the standardID to the
IVOA ID for the ConeSearch standard.
See vr:Capability for documentation on inherited children.
The capabilities of an SIA implementation.
Editor's Notes:
* This is a prototype definition to
illustrate how to extend the schema to a specific
standard interface.
* Staging information is not included yet.
The class of image service: Cutout, Mosaic, Atlas, Pointed
The maximum image query region size, expressed in
decimal degrees. A value of 360 degrees indicates that
there is no limit and the entire data collection
(entire sky) can be queried.
The maximum image query region size, expressed in
decimal degrees. A value of 360 degrees indicates
that there is no limit and the entire data collection
(entire sky) can be requested.
The largest image (in terms of pixels) that can be
requested.
The maximum image file size in bytes.
The largest number of records that the Image Query web
method will return.
a set of query parameters that is expected
to produce at least one matched record which
can be used to test the service.
The maximum size in the longitude (R.A.) direction
The maximum size in the latitdude (Dec.) direction
The sky position in the longitude (R.A.) direction
The sky position in the latitdude (Dec.) direction
The image size in the longitude (R.A.) direction in pixels
The image size in the latitdude (Dec.) direction in pixels
The class of image service: Cutout, Mosaic, Atlas, Pointed
This is a service which extracts or "cuts out" rectangular
regions of some larger image, returning an image of the
requested size to the client. Such images are usually drawn
from a database or a collection of survey images that cover
some large portion of the sky. To be considered a cutout
service, the returned image should closely approximate (or at
least not exceed) the size of the requested region; however,
a cutout service will not normally resample (rescale or
reproject) the pixel data. A cutout service may mosaic image
segments to cover a large region but is still considered a
cutout service if it does not resample the data. Image
cutout services are fast and avoid image degredation due to
resampling.
This service is similar to the image cutout service
but adds the capability to compute an image of the
size, scale, and projection specified by the
client. Mosaic services include services which
resample and reproject existing image data, as well
as services which generate pixels from some more
fundamental dataset, e.g., a high energy event list
or a radio astronomy measurement set. Image mosaics
can be expensive to generate for large regions but
they make it easier for the client to overlay image
data from different sources. Image mosaicing
services which resample already pixelated data will
degrade the data slightly, unlike the simpler cutout
service which returns the data unchanged.
This category of service provides access to
pre-computed images that make up a survey of some
large portion of the sky. The service, however, is
not capable of dynamically cutting out requested
regions, and the size of atlas images is
predetermined by the survey. Atlas images may range
in size from small cutouts of extended objects to
large calibrated survey data frames.
This category of service provides access to
collections of images of many small, "pointed"
regions of the sky. "Pointed" images normally focus
on specific sources in the sky as opposed to being
part of a sky survey. This type of service usually
applies to instrumental archives from observatories
with guest observer programs (e.g., the HST archive)
and other general purpose image archives (e.g., the
ADIL). If a service provides access to both survey
and pointed images, then it should be considered a
Pointed Image Archive for the purposes of this
specification; if a differentiation between the
types of data is desired the pointed and survey data
collections should be registered as separate image
services.
A query to be sent to the service
the right ascension of the search cone's center in
decimal degrees.
the declination of the search cone's center in
decimal degrees.
the verbosity level to use where 0 means the bare
minimum set of columns and 3 means the full set of
available columns.
any extra (particularly non-standard) parameters that must
be provided (apart from what is part of base URL given by
the accessURL element).
this value should be in the form of name=value
pairs delimited with apersands (&).